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Echo Depth Sounding
Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; the resulting time of flight, along with knowledge of the speed of sound in water, allows determining the distance between sonar and target. This information is then typically used for navigation purposes or in order to obtain depths for charting purposes. Echo sounding can also be used for ranging to other targets, such as fish schools. Hydroacoustic assessments have traditionally employed mobile surveys from boats to evaluate fish biomass and spatial distributions. Conversely, fixed-location techniques use stationary transducers to monitor passing fish. The word '' sounding'' is used for all types of depth measurements, including those that don't use sound, and is unrelated in origin to the word ''sound'' in the sense of noise or tone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echo Sounding USN
In audio signal processing and acoustics, an echo is a reflection (physics), reflection of sound that arrives at the listener with a delay after the direct sound. The delay is directly proportional to the distance of the reflecting surface from the source and the listener. Typical examples are the echo produced by the bottom of a well, a building, or the walls of enclosed and empty rooms. Etymology The word ''echo'' derives from the Greek ἠχώ (''ēchō''), itself from ἦχος (''ēchos''), 'sound'. Echo (mythology), Echo in Greek mythology was a mountain nymph whose ability to speak was cursed, leaving her able only to repeat the last words spoken to her. Nature Some animals, such as cetaceans (dolphins and whales) and bats, use echo for location sensing and navigation, a process known as Animal echolocation, echolocation. Echoes are also the basis of sonar technology. Acoustic phenomenon Walls or other hard surfaces, such as mountains and privacy fences, reflect acous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paul Langevin
Paul Langevin (23 January 1872 – 19 December 1946) was a French physicist who developed Langevin dynamics and the Langevin equation. He was one of the founders of the '' Comité de vigilance des intellectuels antifascistes'', an anti-fascist organization created after the 6 February 1934 far right riots. Being a public opponent of fascism in the 1930s resulted in his arrest and being held under house arrest by the Vichy government for most of World War II. Langevin was also president of the Human Rights League (LDH) from 1944 to 1946, having recently joined the French Communist Party. He was a doctoral student of Pierre Curie and later a lover of widowed Marie Curie. He is also known for his two US patents with Constantin Chilowsky in 1916 and 1917 involving ultrasonic submarine detection. He is entombed at the Panthéon. Life Langevin was born in Paris, and studied at the '' École de Physique et Chimie'' and the ''École Normale Supérieure''. He then went to the Univ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fathom
A fathom is a unit of length in the imperial and the U.S. customary systems equal to , used especially for measuring the depth of water. The fathom is neither an international standard (SI) unit, nor an internationally accepted non-SI unit. Historically it was the maritime measure of depth in the English-speaking world but, apart from within the US, charts now use metres. There are two yards (6 feet) in an imperial fathom. Originally the span of a man's outstretched arms, the size of a fathom has varied slightly depending on whether it was defined as a thousandth of an (Admiralty) nautical mile or as a multiple of the imperial yard. Formerly, the term was used for any of several units of length varying around . Etymology The term (pronounced ) derives (via Middle English ''fathme'') from the Old English ''fæðm'', which is cognate with the Danish word ''favn'' and means "embracing arms" or "pair of outstretched arms". It is maybe also cognate with the Old High German wo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International System Of Units
The International System of Units, internationally known by the abbreviation SI (from French ), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official status in nearly every country in the world, employed in science, technology, industry, and everyday commerce. The SI system is coordinated by the International Bureau of Weights and Measures, which is abbreviated BIPM from . The SI comprises a coherent system of units of measurement starting with seven base units, which are the second (symbol s, the unit of time), metre (m, length), kilogram (kg, mass), ampere (A, electric current), kelvin (K, thermodynamic temperature), mole (mol, amount of substance), and candela (cd, luminous intensity). The system can accommodate coherent units for an unlimited number of additional quantities. These are called coherent derived units, which can always be represented as products of powers of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Velocity Probe
A sound velocity probe is a device that is used for measuring the speed of sound, specifically in the water column, for oceanographic and hydrographic research purposes. History Early depth sounding was achieved using lead line sounding (or sounding line), where a lead weight attached to a length of rope marked with depth values. As this method was mechanical in nature, the only correction that was applied to the sounding was the reduction of the sounding for tidal height. In the mid 20th century, sonar systems were developed to allow the measurement of underwater distances using the two way travel time of an acoustic pulse. This allowed the surveyor to take many more soundings in a given period of time and was less labor intensive than using a lead line. Use For many applications of sonar the speed of sound can be assumed to be an average speed of 1500 meters per second. However, the speed of sound in seawater can vary from 1440 to 1570 meters per second., UN Atlas of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrography
Hydrography is the branch of applied sciences which deals with the measurement and description of the physical features of oceans, seas, coastal areas, lakes and rivers, as well as with the prediction of their change over time, for the primary purpose of safety of navigation and in support of all other marine activities, including economic development, security and defense, scientific research, and environmental protection. History The origins of hydrography lay in the making of charts to aid navigation, by individual mariners as they navigated into new waters. These were usually the private property, even closely held secrets, of individuals who used them for commercial or military advantage. As transoceanic trade and exploration increased, hydrographic surveys started to be carried out as an exercise in their own right, and the commissioning of surveys was increasingly done by governments and special hydrographic offices. National organizations, particularly navies, realize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Principle Of SBES
A principle may relate to a fundamental truth or proposition that serves as the foundation for a system of beliefs or behavior or a chain of reasoning. They provide a guide for behavior or evaluation. A principle can make values explicit, so they are expressed in the form of rules and standards. Principles unpack the values underlying them more concretely so that the values can be more easily operationalized in policy statements and actions. In law, higher order, overarching principles establish rules to be followed, modified by sentencing guidelines relating to context and proportionality. In science and nature, a principle may define the essential characteristics of the system, or reflect the system's designed purpose. The effective operation would be impossible if any one of the principles was to be ignored. A system may be explicitly based on and implemented from a document of principles as was done in IBM's 360/370 ''Principles of Operation''. It is important to differen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fessenden Oscillator
A Fessenden oscillator is an electro-acoustic transducer invented by Reginald Fessenden, with development starting in 1912 at the Submarine Signal Company of Boston. It was the first successful acoustical echo ranging device. Similar in operating principle to a dynamic voice coil loudspeaker, it was an early kind of transducer, capable of creating underwater sounds and of picking up their echoes. The creation of this device was motivated by the RMS ''Titanic'' disaster of 1912, which highlighted the need to protect ships from collisions with icebergs, obstacles, and other ships. Because of its relatively low operating frequency, it has been replaced in modern transducers by piezoelectric devices. Oscillator The ''oscillator'' in the name referred to the fact that the device vibrated and moved water in response to a driving AC current. It was not an electronic oscillator but a mechanical one in that it generated repetitive mechanical vibrations. Electronic oscillators did ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
English Channel
The English Channel, also known as the Channel, is an arm of the Atlantic Ocean that separates Southern England from northern France. It links to the southern part of the North Sea by the Strait of Dover at its northeastern end. It is the busiest Sea lane, shipping area in the world. It is about long and varies in width from at its widest to at its narrowest in the Strait of Dover."English Channel". ''The Columbia Encyclopedia'', 2004. It is the smallest of the shallow seas around the continental shelf of Europe, covering an area of some . The Channel aided the United Kingdom in becoming a naval superpower, serving as a natural defence against invasions, such as in the Napoleonic Wars and in the World War II, Second World War. The northern, English coast of the Channel is more populous than the southern, French coast. The major languages spoken in this region are English language, English and French language, French. Names Roman historiography, Roman sources as (or , ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toulon
Toulon (, , ; , , ) is a city in the Provence-Alpes-Côte d'Azur region of southeastern France. Located on the French Riviera and the historical Provence, it is the prefecture of the Var (department), Var department. The Commune of Toulon has a population of 176,198 people (2018), making it France's 13th-largest city. It is the centre of an urban unit with 580,281 inhabitants (2018), the ninth largest in France by population. Toulon is the second largest French city by urban area on the Mediterranean coast after Marseille. Toulon is an important centre for naval construction, fishing, wine making, and the manufacture of aeronautical equipment, armaments, maps, paper, tobacco, printing, shoes, and electronic equipment. The military port of Toulon is the major navy, naval centre on France's Mediterranean coast, home of the French aircraft carrier ''French aircraft carrier Charles de Gaulle, Charles de Gaulle'' and her battle group. The French Mediterranean Fleet is based in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piezoelectricity
Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The piezoelectric effect results from the linear electromechanical interaction between the mechanical and electrical states in crystalline materials with no inversion symmetry. The piezoelectric effect is a reversible process: materials exhibiting the piezoelectric effect also exhibit the reverse piezoelectric effect, the internal generation of a mechanical strain resulting from an applied electric field. For example, lead zirconate titanate crystals will generate measurable piezoelectricity when their static structure is deformed by about 0.1% of the original dimension. Conversely, those same crystals will change about 0.1% of their static dimension when an external electric field is applied. The inverse piezoelectric effect is used in the pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
